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This Article Full Text Full Text (PDF) All Versions of this Article: 297/5/R1601    most recent 91034.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wenzel, J. Articles by Jöhren, O. PubMed PubMed Citation Articles by Wenzel, J. Articles by Jöhren, O.

Articles

Hypocretin/orexin increases the expression of steroidogenic enzymes in human adrenocortical NCI H295R cells

¹Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany; ²Warwick Medical School, Warwick University, Coventry, United Kingdom; and ³Carl Gustav Carus University Hospital, Medical Clinic III, University of Dresden, Dresden, Germany

Submitted December 19, 2008 ; accepted in final form September 28, 2009

Hypocretins/orexins act through two receptor subtypes: OX₁ and OX₂. Outside the brain, orexin receptors are expressed in adrenal glands, where orexins stimulate the release of glucocorticoids. To further address the regulation of steroidogenesis, we analyzed the effect of orexins on the expression of steroidogenic enzymes in human adrenocortical National Cancer Institute (NCI) H295R cells by qPCR. In NCI H295R cells, OX₂ receptors were highly expressed, as they were in human adrenal glands. After treatment of NCI H295R cells with orexin A for 12–24 h, the cortisol synthesis rate was significantly increased, whereas 30 min of treatment showed no effect. While CYP11B1 and CYP11B2 mRNA levels were increased already at earlier time points, the expression of HSD3B2 and CYP21 mRNA was significantly up-regulated after treatment with orexin A for 12 h. Likewise, orexin B increased CYP21 and HSD3B2 mRNA levels showing, however, a lower potency compared with orexin A. The mRNA levels of CYP11A and CYP17 were unaffected by orexin A. OX₂ receptor mRNA levels were down-regulated after 12 and 24 h of orexin A treatment. Orexin A increased intracellular Ca²⁺ but not cAMP concentrations in NCI H295R cells. Furthermore, inhibition of PKC and MAPK kinase/ERK kinase (MEK1/2) prevented the increase of HSD3B2 expression by orexin A. Accordingly, orexin A treatment of NCI H295R cells markedly enhanced ERK1/2 phosphorylation that was prevented by PKC and, in part, PKA inhibition. In conclusion, orexins may influence adrenal steroidogenesis by differential regulation of the expression of steroidogenic enzymes involving Ca²⁺, as well as PKC-ERK1/2 signaling.

hypocretin-1 and -2; OX₁ and OX₂ receptor; real-time reverse transcriptase-polymerase chain reaction; cortisol